This invention relates to a method to devolatilize polymer with a rotary disk processor. The disk processor can be as disclosed in U.S. Pat. Nos. 4,194,841 and 4,142,805, both hereby incorporated by reference. The method of the invention is used to remove reaction by-products, and unreacted components such as ethylene glycol and monomers and undesirable by-products such as oligomers from relatively high viscosity molten polymers, particularly polyester and nylon polymers. Removal of the volatile component makes possible a polymer which can be spun into fiber, extruded as film or shaped into other shaped objects.
Preparation of polyester and particularly a thermally stabilized polyethylene terephthalate (PET) is taught in U.S. Pat. No. 4,171,422, hereby incorporated by reference. Other methods of creating low carboxyl polyesters are taught in Japanese Pat. No. 41 713 to Shima et al. and U.S. Pat. No. 2,863,854 to Wilson, hereby incorporated by reference. These methods can create volatile by-products, such as carbon dioxide, which form bubbles which would destroy the integrity of the final shaped product such as fiber. The volatile by-products must be removed quickly to prevent degradation of the molten polymer and regain of carboxyl groups. Special engineering has been utilized in the past to shorten the time of transit between formation of the desired polymer in molten state and the spinning or other shaping apparatus. See U.S. Pat. No. 4,072,663, hereby incorporated by reference. In order that the polymer, particularly polyester, is protected from degradation, additives such as to create low carboxyl group levels and thermal stability, should be added at the last possible point in the processing apparatus, such as the final finisher as described in the prior art U.S. Pat. Nos. 3,976,431; 3,728,083 and Re. 28,937, all hereby incorporated by reference.
Preparation of nylon polymer is described in U.S. Pat. Nos. 3,294,756; 3,813,366 and 3,578,640, all hereby incorporated by reference. Here the problem of the prior art has been efficient removal of the monomer and oligomers left in the polymer just prior to shaping, spinning or extruding it. Prior art methods and apparatus are bulky, expensive and do not always lower the monomer and oligomer content sufficiently, particularly when the molten polymer is shaped or extruded (spun) from the molten state, rather than forming solid particles which could be washed with water to remove monomer and oligomers. By "relatively high viscosity" is meant polymer of viscosity high enough to be shaped, spun, extruded or the like, preferably nylon of viscosity above 35 relative viscosity, and polyester above 0.72 intrinsic viscosity.